So does anyone know why my games often freeze at loading screens after playing a game for about 45mins?

mods argue too much huh........
if you are certain you have a magic3 (not 3.1) then that most likely is your problem........the magic3 had overheating problems and caused games to freeze. i personally had a magic3 and most my games would freeze, i remember playing smackdown with my bro and after the first fight it would freeze. some people fixed this by adding a switch to turn off the chip after the game booted.
then the official magic team released a new chip (magic3.1) to fix the problem, but all they did was make the chip turn off right after boot which just caused more problems with v7 protected games.
so in conclusion: your problem is most likely the chip itself.